A large creature stands on four stiltlike legs. It has a birdlike body, round and plump, about the size of a small pony, balanced atop its legs. Feathers that range in color from brown to red cover its body, and its terrible claws and beak glint like burnished metal.

Achaierais are massive, 15-foot-tall flightless birds that inhabit the plane of Acheron and are only occasionally encountered elsewhere. They are evil, clever, and predatory, with a distinct taste for torture.
Achaierais speak Infernal. They weigh about 750 pounds.

COMBAT

In close combat, an achaierai lashes out with two of its four legs and snaps with its powerful beak. It makes frequent use of its Spring Attack feat to strike quickly and then retreat out of range before an enemy can counterattack.
An achaierai’s natural weapons, as well as any weapons it wields, are treated as evil-aligned and lawful-aligned for the purpose of overcoming damage reduction.Black Cloud (Ex): Up to three times per day an achaierai can release a choking, toxic black cloud. Those other than achaierai within 10 feet instantly take 2d6 points of damage. They must also succeed on a DC 15 Fortitude save or be affected for 3 hours as though by an insanity spell (caster level 16th). The save DC is Constitution-based.